The manufacture and use of metal dispensing containers with a dudgeoned valve have disadvantages.
Firstly, during manufacture, the clamp and possibly the machine have to be changed, and the type of cup has to be changed so that plastic and metal distributing containers can be produced in succession. This means that there are interruptions in the production line and a double stock of crimping equipment and valves are required.
Secondly, dudgeoning is a tricky operation, more difficult than external crimping.
And finally, dispensing containers with an externally crimped valve cup generally have a better seal than those with a dudgeoned valve cup.
To avoid these disadvantages, applicants naturally tried to proceed to crimp valve cups externally onto large metal containers by the method conventionally used for medium size metal containers and plastic containers.
This conventional method comprises:
selecting a valve cup where the part which goes into the neck has an outside diameter substantially equal to the inside diameter of the neck, the outside diameter of the cup of the valve however being slightly less, typically 0.2 mm less, than the inside diameter of the neck in order to facilitate insertion.
placing an annular seal on the edge of the neck.
inserting the valve cup in the container.
turning in the outer skirt of the cup below the edge of the neck with a crimping clamp, thus causing the cup and seal to be gripped.
By using this known method, applicants did indeed obtain large metal dispensing containers with a crimped valve cup. However, tests carried out on samples thus obtained showed that the degree of tightness normally found in medium size metal dispensing containers with a crimped valve cup was not achieved. The same tests showed that the samples of large metal dispensing containers obtained, with a crimped valve cup, were no better sealed than dispensing containers of the same size with a dudgeoned valve cup.
The problem raised was thus to improve the degree of sealing tightness of large metal dispensing containers with an externally crimped valve cup.
Applicants have succeeded to solve the problem by modifying the assembly for the container with the valve cup.